The production of interferon-γ (IFN-γ) in immunocytes is an important step in early-stage self-defense and tumor control against virus and bacterial infection (Biron, C. A. et al., Annu. Rev. Immunol. 1999, 17, 189-220). IFN-γ is produced in natural killer (NK) and natural killer T (NKT) cells that are generally used as effector cells in regulating immune reactions (Schoenborn, J. R. et al., Adv. Immunol. 2007, 96, 41-101). IFN-γ expression is particularly related to a pro-inflammatory state. The biological role of cytokain IFN-γ in a defense system is well known, and the role is related to both virus replication and direct suppression of immunostimulation (Gessani, S. et al., Cytokine & Growth F. R. 1998, 9, 117-123; Goodbourn, S. et al., J. Gen. Virol. 2000, 81, 2341-2364).
Pharmaceutical markets have grown globally due to an increase in income, aging population, increased demand for chronic disease-related medicines, life expectancy increase and the like, and as a result, research and development on biopharmaceuticals have increased in pharmaceutical industries at home and abroad. Among other things, there has been increased demand for antiviral therapeutic agent-related research that is the base of the development of AIDS therapeutic agents, and liver disease and influenza disease therapeutic agents, which are problems needed be solved for all mankind, for the development of therapeutic agents utilizing the results of the research, and for the development of medical technologies and technologies for improving quality of life, have been increased.
A virus is a small infectious agent (average of 0.1 μm or less) that is smaller than bacteria and thereby cannot be filtered even with a bacterial filter (0.22 μm), and is an organism that has only nucleic acid (DNA or RNA) and a small number of proteins as substances needed for survival, and thereby are dependent upon hosts. As therapeutic agents for diseases caused by viruses, drugs that weaken or kill the action of viruses infested into the body are referred to as antiviral therapeutic agents.
Immunotherapy using a vaccine is currently a mainstream viral infectious disease treatment. Specifically, examples of therapeutic agents for the infectious disease caused by chlamydia (giant virus) such as trachoma and fourth venereal disease (venereal disease) comprise tetracycline and chloramphenicol, the examples of a preventive agent for influenza A-type virus include amantadine, an idoxuridine (IDU) eye bath drop was developed as a preventive agent for herpes keratitis, and vidarabine/acyclovir have received attention as a simple herpes encephalitis (encephalitis) or an immunosuppressant. Particularly, interferon is a most promising drug for viral infectious diseases, and utility thereof is currently being examined.
Lately, the preference for natural substances in treating or preventing health issues has grown globally. This trend is affecting pharmaceutical companies, in that they are producing new antimicrobial agents extracted from plants. Accordingly, research on exploring new anti-viral materials from thousands of plant types has been constantly carried out globally, and various phytochemicals having antiviral activities, such as flavonoid, terpenoid, lignan, sulfide, polyphenols, coumarin, saponin, alkaloid, polyyne, thiophene, proteins and peptides have been identified. Several volatile essential oils of generally used edible herbs, spices and herb teas also have antiviral activities. However, with the exception of a few compound groups described above, most research on the active substances of medicinal plants having antiviral activities is in its beginning stages.
Euphorbia kansui Liou (Euphorbiaceae) is widely distributed throughout the China and Korea mainlands. Dried roots of Euphorbia kansui Liou, also known as “kansui”, have been used as herbal remedies for edema and ascites (Wang, L. Y. et al., J. Nat. Prod. 2003, 66, 630-633), and cancer (Wang, L. Y. et al., J. Nat. Prod. 2002, 65, 1246-1251). Through the previous studies on Euphorbia kansui Liou, the presence of a great number of euphan-type triterpenes (Chang, J. S. et al., Planta Med. 2010, 76, 1544-1549), ingenane-type diterpenes (Pan, Q. et al., J. Nat. Prod. 2004, 67, 1548-1551) and jatrophane-type diterpenes (Zheng, W. F. et al., Planta Med. 1998, 64, 754-756) was identified in the extract of Euphorbia kansui Liou. In addition, the samples were verified to have an anti-cancer effect (Pan, Q. et al., J. Nat. Prod. 2004, 67, 1548-1551), a cytostatic effect (Chang, J. S. et al., Planta Med. 2010, 76, 1544-1549) and an anti-allergic effect (Ott, H. H. et al., Experientia. 1981, 37, 88-91).